Cyclopentasilane is a known compound that is liquid at ambient temperatures and can form silicon films with useful photovoltaic or electrical properties. However, cyclopentasilane is relatively volatile, and there has been a recent interest in methods of forming higher molecular weight silanes that have similar chemical properties, but that are less volatile at ambient temperatures.
FIG. 1A shows an equation for the catalytic dehydrogenative polymerization of cyclopentasilane by a Zr catalyst such as Cp2ZrR2 (Cp=cyclopentadienyl; R=H, alkyl, aryl or trialkylsilyl). The product is a polysilane with relatively high molecular weight, but which can be intractable or insoluble, even in nonpolar organic solvents. It is believed that Zr complexes (and other early transition metal-based catalysts) tend to form polysilanes with an undesirably high degree or incidence of branching, which can make the polysilane less soluble, and in the extreme case, insoluble.
FIG. 1B shows an equation for the idealized catalytic dehydrogenative polymerization of cyclopentasilane. The polymerized product contains substantially linear poly(cyclopentasilane), with a minimum (or no) branching. Such a poly(cyclopentasilane) is expected to be relatively soluble in nonpolar solvents, and could increase the viscosity of an ink containing the poly(cyclopentasilane) to further facilitate processes of coating or printing the ink on a substrate. However, in practice, actual cyclopentasilane polymers have appreciable and/or significant branching and/or cross-linking Thus, a need and/or desire for an improved (cyclo)silane polymerization process is felt.